PHIYER8ITY  OF  CALIFOBNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY.  CALIFORNIA 


ALMOND  POLLINATION 


BY 

WARREN  P.  TUFTS 


BULLETIN  No.    306 

March,  1919 


UNIVERSITY  OF  CALIFORNIA  PRESS 
BERKELEY 

1919 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 

heads  of  divisions 
Thomas  Forsyth  Hunt,  Director. 
Edward  J.  Wickson,  Horticulture  (Emeritus). 

Herbert  J.  Webber,  Director  Citrus  Experiment  Station;  Plant  Breeding. 
Hubert  E.  Van  Norman,  Vice-Director;  Dairy  Management. 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 
Charles  W.  Woodworth,  Entomology. 
Ralph  E.  Smith,  Plant  Pathology. 
J.  Eliot  Coit,  Citriculture. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shav^,  Soil  Technology. 

John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Enology. 
Warren  T.  Clarke,  Agricultural  Extension. 
John  S.  Burd,  Agricultural  Chemistry. 
Charles  B.  Lipman,  Soil  Chemistry  and  Bacteriology. 
Clarence  M.  Haring,  Veterinary  Science  and  Bacteriology. 
Ernest  B,  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
James  T.  Barrett,  Plant  Pathology. 
Fritz  W.  Woll,  Animal  Nutrition. 
Walter  Mulford,  Forestry. 
W.  P.  Kelley,  Agricultural  Chemistry. 
H.  J.  QuAYLE,  Entomology. 
J.  B.  Davidson,  Agricultural  Engineering. 
Elwood  Mead,  Rural  Institutions. 
H.  S.  Reed,  Plant  Physiology. 
J.  C.  Whitten,  Pomology. 
fFRANK  Adams,  Irrigation  Investigations. 
C.  L.  RoADHOUSE,  Dairy  Industry. 
Frederick  L.  Griffin,  Agricultural  Education. 
John  E.  Dougherty,  Poultry  Husbandry. 
S.  S.  Rogers,  Olericulture. 
J,  G.  Moodey,  Assistant  to  the  Director. 
Mrs.  D.  L.  Bunnell,  Librarian. 

DIVISION  OF  POMOLOGY 

J.  C.  Whitten  *E.  L.  Overholser 

W.  L.  Howard  W.  P.  Tufts 

R.  II.  Taylor  W.  L.  Sweet 

A.  H.  Hendrickson  G.  L.  Philp 

M.  N.  Wood 


t  In  co-operation  with  office  of  Public  Roads  and  Rural  Engineering,  U.   S. 
Department  of  Agriculture. 

*  Exchange  professor  from  Cornell  University  for  1918-19. 


ALMOND   POLLINATION 

By  WAKKEN  p.  TUFTS 


For  the  successful  production  of  orchard  crops  there  are  certain 
important  limiting  factors  to  be  considered.  In  the  culture  of  the 
almond  freedom  from  late  spring  frosts,  a  deep  and  well-drained  soil, 
and  the  interplanting  of  proper  varieties  to  secure  cross-pollination, 
are  the  chief  ''limiters." 

Almonds  were  planted  in  California  as  early  as  1853,  but  records 
show  that  the  tonnage  of  the  early  orchards  was  quite  variable.  The 
failure  of  these  plantations  was  due  largely  to  a  lack  of  knowledge  of 
the  factors  controlling  the  successful  production  of  the  almond.  Grad- 
ually it  became  a  recognized  fact  that  the  almond,  on  account  of  its 
early  blooming  habit  (in  certain  sections  of  California  sometimes  as 
early  as  late  January),  and  its  aversion  to  heavy  and  poorly-drained 
soils,  would  succeed  commercially  only  in  certain  locations — that  is, 
where  there  is  little  danger  from  late  spring  frosts  and  where  the 
soil  is  deep  and  well  drained. 

That  there  is  a  distinct  pollination  problem  with  the  almond  was 
recognized  as  early  as  1885,  when  Mr.  A.  T.  Hatch,^  of  Suisun,  Cali- 
fornia, pointed  out  the  fact  that  Languedoc  trees  near  seedlings  always 
produced  heavier  crops  than  when  planted  in  solid  blocks.  On  account 
of  its  reputation  for  light  bearing  the  Languedoc  variety  was  rapidly 
displaced  by  the  Nonpareil,  I.  X.  L.,  and  Ne  Plus  Ultra  varieties, 
seedlings  originated  and  introduced  by  Mr.  Hatch  in  the  early  90 's. 
Many  of  the  later  orchards  also  were  planted  in  unsuitable  places, 
there  being  a  feeling  that  these  new  improved  varieties  would  prove 
profitable  under  all  conditions.  In  addition  to  the  failure  of  the 
orchards  planted  in  unfavorable  locations,  many  instances^  are  on 
record  as  to  the  non-bearing  of  the  Hatch  varieties  where  the  only 
plausible  explanation  is  that  of  lack  of  proper  cross-pollination. 

THE   PROBLEMS   OF  ALMOND    POLLINATION 

In  carrying  out  the  work  of  which  this  bulletin  is  a  progress  report, 
an  attempt  was  made  to  solve  the  following  problems  for  California 
conditions : 


1  California  State  Board  of  Horticulture  Eeports,  1885-1886,  p.  326. 

2  Dargitz,  J.  P.,  Pacific  Eural  Press,  vol.  72,  no.  10,  Sept.  8,  1906. 


338  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

1.  What  varieties  of  almonds  commercially  grown  in  California 
will  be  profitable  when  planted  in  solid  blocks — i.e.,  without  pollen- 
izers  ?    This  is  a  question  of  self-f ertility.* 

2.  What  varieties  planted  in  solid  blocks  will  not  be  profitable? 
This  is  a  question  of  self -sterility.* 

3.  If  the  commercial  varieties  of  almonds  at  present  grown  in 
California  will  not  produce  profitably  without  providing  for  cross- 
pollination,  which  varieties  should  be  planted  together?  This  is  a 
question  of  inter-fertility. 

Even  though  two  varieties  may  be  inter-fertile,  the  following  points 
should  always  be  considered  in  selecting  pollenizing  varieties : 

(a)   Commercial  value  of  the  pollenizer. 

(6)  Coincidence  of  bloom  of  the  pollenizer  with  the  variety  to  be 
pollinated. 

(c)  Succession  of  ripening  of  varieties  for  convenience  in  har- 
vesting. 

(d)  Amount  of  pollen  produced  by  the  pollenizer. 

(e)  Germinability  of  the  pollen  produced  by  the  pollenizer. 

ORGANIZATION    OF  THE   WORK 

The  methods  employed  for  the  solution  of  the  problems  just  out- 
lined were  those  commonly  in  use  in  cross-pollination  experiments.^ 
Briefly  stated,  this  part  of  the  work  consisted  in  the  application  by 
hand  of  the  pollen  desired,  having  first  removed  the  flowers'  own 
pollen-producing  organs  (the  stamens).  The  introduction  of  foreign 
pollen  through  the  agency  of  wind  and  insects  was  prevented  by  cov- 
ering the  hand-pollinated  blossoms  with  paper  sacks.  Accurate  counts 
of  the  flowers  of  the  various  varieties  thus  treated  with  pollen  of 
different  kinds  were  made  and  recorded.  Later  in  the  season  the  sacks 
were  removed.  The  fruits  resulting  from  these  artificial  pollinations 
were  counted  and  the  proper  records  made  after  the  first  and  second 
drops  and  again  at  harvest. 

During  1910  the  work  was  carried  on  by  B.  S.  Brown,*  and  during 

3  The  Division  of  Pomology  has  in  preparation  a  bulletin  dealing  with  the 
more  technical  phases  of  the  whole  pollination  question.  In  this  publication  the 
''technique"  employed  in  the  solution  of  various  pollination  problems  will  be 
discussed  in  detail. 

4  Brown,  B.  S.,  Almond  Culture,  a  thesis  presented  as  partial  fulfillment  of 
the  requirements  for  the  Master's  degree  from  the  University  of  California,  1911. 

*  The  writer  prefers  the  terms,  * '  barren ' '  and  * '  fruitful, ' '  as  explained  by 
Kraus  in  the  Journal  of  Heredity,  vol.  6,  no.  12,  pp.  549-557,  rather  than  the 
inexact  terms,  "sterile"  and  "fertile."  The  latter  terms  have  been  used  in 
this  paper,  due  to  the  fact  that  the  general  public  is  more  or  less  familiar  with 
these  expressions  as  herein  used. 


ALMOND  POLLINATION  339 

1915  by  W.  E.  Gilfillan.^  The  data  for  these  two  years  are  of  little 
value  in  themselves,  because  the  numbers  employed  were  relatively 
small.  During  1916  the  work  was  largely  confined  to  the  determina- 
tion of  the  question  of  self-sterility,  and  in  1917  the  same  work  was 
repeated  and  many  cross-pollinations  made.  In  1918  repetition  of 
all  self-pollinations  and  crosses  was  again  made,  but  frost  in  the 
University  orchards  at  Davis  vitiated  the  whole  season's  effort  with 
the  exception  of  the  experiments  performed  on  the  Nonpareil  variety 
which  were  carried  on  in  the  orchard  of  Mr.  G.  W.  Pierce,  some  six 
miles  distant  from  the  University  Farm. 

With  the  exception  just  noted  all  experiments  were  conducted  in 
the  University  orchards  at  Davis.  The  trees  in  the  University  orchard 
are  all  young  and  vigorous,  having  been  planted  during  the  spring  of 
1908.  In  the  Pierce  orchard  the  trees  are  in  fair  vigor.  This  orchard 
was  planted  in  1892. 

THE    BLOOMING    PERIOD    OF    CERTAIN    ALMOND    VARIETIES 

Almonds  have  a  relatively  long  period  of  bloom  if  the  total  time 

from  the  opening  of  the  first  blossoms  to  the  shedding  of  the  petals 

is  considered.     Many  growers  are  of  the  opinion  that  even  the  later 

blooming  varieties  overlap  sufficiently  with  the  earlier  varieties  to  set 

a  crop  on  the  latter.     Such  a  selection  of  varieties,  however,  is  not 

to  be  generally  advised,  although  in  some  cases  it  may  be  desired  to 

use  a  variety  listed  as  an  early  bloomer  to  pollenize  a  late  bloomer. 

Based  on  what  may  be  called  the  period  of  effective  bloom,  varieties 

may  be  roughly  divided  into  early  and  late  bloomers  as  shown  in  the 

following  lists.     The  Nonpareil  has  been  included  in  both  lists  as 

being  just  about  midway: 

Earljj  Bloomers  Late  Bloomers 

Big  White  Flat  Dickinson 

California  Drake 

Harriott  Eureka 

I,  X.  L.  Golden  State 

Jordan  Languedoc 

King  Nonpareil 

Klondike  Eeams 

Lewelling  Sellers 

Ne  Plus  Ultra  Texas 
Nonpareil 
Peerless 
Princess 
Silver  Shell 


5  Gilfillan,  W.   E.,  Pollination   of  the   Almond,   a   thesis  presented   as  partial 
fulfillment  of  the  requirements  for  the  Bachelor 's  degree  from  the  University  of 


California,  1915. 


340 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 


The  accompanying  chart  (page  341)  gives  the  average  blooming 
seasons  of  certain  almond  varieties  for  the  years  1914  to  1918,  inclu- 
sive, unless  otherwise  noted.  The  date  of  bloom  is  of  course  dependent 
on  many  factors,  such  as  soil,  season  and  location. 


Period   of     Effective   Blojjdninc-:  <^'f   Ahiiondj-Univerjity  K\rni~l*]117- 

FEBRUARY  *•       MARCH         ^ 


Harriett 

NePluj  Ultra 

l.X.L. 

PeerJejj' 

Jordev.n 

Prmcejj 

Lewelling 

California 

Kill  a 

a 

Won  pare  il 
Golden  JIate 
brake 

La/]cuiedoc 
Texau" 


12 

13  l4|l5i(fe|l7|l8|l'?ko|2l|Z2|23|24|25|2fc|27|28|  1 

2 

3 

-.1 

5 

Q, 

7 

8 

■? 

10 

II 

12 

13 

1^ 

15 

lb 

17 

18 

19 

20 

21 

22 

23 

■■ 

■ 

m 

m 

■ 

^ 

■ 

■1 

■ 

■ 

■ 

■ 

B 

■ 

■ 

m 

1      1       [       1       1       1       1       !       1       i 

■ 

■ 

■ 

1      1      1      1     {      1     1      i      1      1      !      1 

■ 

1      !      1      1      I      1      1      1      1      1      1      1      !      1 

■ 

■ 

J 

J 

■ 

It 

13 

T5" 

Ts 

Ih 

Tf 

is 

IT 

20 

IT 

22j 

23 

Z") 

25 

Zfo 

27 

28 

T 

aja 

^ 

5 

X 

I 

tl 

T 

T 

II   12  13  1^  I5|uil7  18 

!<?  20.2  122 

Ti 

Fig.  1. — The  effective  blooming  period  of  certain  almond  varieties  during  the 
season  of  1917.  The  dates  in  this  table  cover  the  time  each  variety  was  in 
conspicuous  bloom  and  therefore  of  maximum  attraction  to  insects. 


POLLEN    PRODUCTION   OF  ALMOND   VARIETIES 

In  addition  to  the  inquiry  into  the  viability  of  the  pollen  produced 
and  the  date  of  bloom  of  a  certain  variety,  the  orchardist  in  selecting 
a  pollenizer  for  his  commercial  orchard  must  take  into  consideration 
whether  the  variety  to  be  planted  as  a  pollenizer  is  a  good  pollen 
producer.  In  practically  all  instances  the  pollen  production  of  the 
first  almond  blossoms  was  noted  to  be  quite  inferior  in  quantity  to 
that  produced  by  flowers  maturing  several  days  later. 

Data  covering  the  abundance  of  pollen  production  have  been  col- 
lected for  only  two  seasons.    The  results  are  presented  herewith. 


Pollen  Production  of  Seventeen  Almond  Varieties 

Variety  Pollen  production,  1917 

Big  White  Flat  Abundant 

California  Abundant 

Very  abundant 

Abundant 

Abundant 

Abundant 


Drake 

Golden  State 
Harriott 
I.  X.  L. 


Pollen  production,  1918 
Very  abundant 
Very  abundant 
Very  abundant 
Medium  to  shy 
Abundant 
Abundant 


ALMOND  POLLINATION 


341 


a 

00 

irl- 

►^ 

ri 

1— •• 

n 

UQ 

n 

• 

m 

to 

O 

1 

Hs 

1 

H 

P5 

ts- 

< 

o 

(T> 

p 

^ 

< 

(n 

n> 

»3 

^ 

•-J 

p 

U) 

OTQ 

O 

H^ 

P 

cr 

n- 

(D 

fD 

CO 

o 

Ms 

a' 

CD 

CD 

o 

Hs 

r/5 

<-t- 

»-«J 

C6 

t— i 

P 

P 

^ 

«} 

W 

c^ 

^* 

p 

P 
QTQ 

CD 

Hs 

I-" 

o- 

U3 

o 

CS 

o 

t3- 

o 

3 

^ 

o 

p 

Hs 

l-l- 

c:> 

e 

CD 

M 

rn 

M* 

CD 

P 

Tl 

P 

P 

p— 1 

P 

3 

H- 

o 

CD 

3 

rs 

O- 

o 

1—" 

<1 

c 

P 

3 

H 

t3 

CD 

H- 

Hs 
O 

CO 

CD 
P 

o 

CD 
H 

<J 

t3 

P 

0^ 

CD 

p 

trt- 

^►TS 

• 

CD 

►^ 

o 


CD 
P 
H 
►— • 

*^ 
P 


3::3o^-r  r C)S:^p 53 ^xx os^ c_ n-^ rngd ^^ 

§3    N<    p 
c_n  -t^   c_n    <-n   Oj  C«»J  c_n   on    <-n    **.    Cn    c^  C_n   en    «-»>C-7»—     OJCnOi^^             ^ 

^ 

1    O 

CI]  ^    H 
X»  7)    O 

•<^  o 

o  rn 

:^  M 

X3  —  •a 

o 

— 

ON 

-i- 

— 

- 

— 

=N 

T 

= 

1      1 

1 

71 

^■~ 

-f 

i 

■n 

— 

1 

— 

-> 

■  -n  r 

T 

— 

1 

-^     P 

y 

n 

— 

1 

— 

1- 

P 

— 

H 

■     -^    IT    ■ 

— 

-^ 

— 

H 

— 

T  _  _ 

Si 

do 

K  1- 

^ 

T 

— 

* 

^ 

N, 

?5 

m 

-i 
m 

en 

V 

0! 

^ 

I      1 

^ 

1  r 

_^ 

■      1 

^ 

^ 

1 

§ 

342 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 


Pollen  Production  of  Seventeen  Almond  Varieties — (Continued) 


Variety 
Jordan 
King 
Klondike 
Languedoc 
Lewelling 
Ne  Plus  Ultra 
Nonpareil 
Peerless 
Princess 
Eeams 
Texas 


Pollen  production,  1917 
Medium  to  shy 
Medium 
Abundant 
Very  shy 
Abundant 
Abundant 
Abundant 
Abundant 
Abundant 
Abundant 
Medium  to  abundant 


Pollen  production,  1918 
Shy 

Medium 
Medium 
Medium  to  shy 
Medium 
Abundant 
Abundant 
Abundant 
Abundant 
Abundant 
Abundant 


GERMINABILITY    OF    THE    POLLEN    USED 

The  pollen  used  in  all  experiments  was  in  prime  condition  and 
showed  in  all  cases  quite  a  satisfactory  artificial  germination  test.  In 
many  instances  pollen  collected  from  early  maturing  flowers  proved 
to  be  of  very  poor  viability  as  compared  with  that  produced  by  later 
blossoms  on  the  same  tree. 

Table  I. — Germinability  of  Pollen,  Seasons  1915-1918 

Figures  give  per  cent  germination  in  12  per  cent  cane  sugar  solution 

Variety  1915  1916  1917  1918 

Big  White  Flat .-  93  76 

California 75  37  77 

Dickinson   ....  51 

Drake 94  35  33  32 

Eureka    ....  ....  14 

Golden  State  -.  25  32 

Harriott    92  76  80  88 

I.  X.  L 85  80  94  60 

Jordan  73  50  85  64 

King  80  33  48 

Klondike  ....  89  86 

Languedoc 44  28  12  15 

Lewelling    88  90  69  65 

Ne  Plus  Ultra 89  83  94  74 

Nonpareil   90  88  53  44 

Peerless  50  24  60 

Princess    81  63  39  37 

Eeams  90  ....  53 

Sellers  ....  ....  64 

Texas  85  86  60  16 

Average    82.1  69.5  57.1  52.8 

During  the  first  two  seasons  weather  conditions  during  the  bloom- 
ing period  of  almonds  were  quite  favorable  for  the  setting  of  fruit 


ALMOND  POLLINATION  343 

and,  as  a  consequence,  very  high  germination  tests  were  recorded. 
During  1917  and  1918,  however,  wind,  cold  and  rain  destroyed  to  a 
marked  degree  the  viability  of  the  pollen.  But  inasmuch  as  only  one 
viable  pollen  grain  is  actually  necessary  to  effect  fertilization,  and 
since  by  actual  count  it  was  determined  that  from  sixty  to  one  hundred 
and  twenty-five  pollen  grains  were  deposited  on  the  stigma  of  each 
fiower  artificially  pollinated,  there  need  be'  no  fear  as  to  the  accurac}^ 
of  the  results  during  the  latter  two  seasons,  due  to  low  viability  of  the 
pollen  employed. 

RELATION   OF  NORMAL  SET  TO   FINAL  CROP 

Immediately  after  the  petals  fall  each  flower  begins  to  form  a  fruit. 
During  the  following  two  or  three  weeks  a  certain  percentage  of  these 
young  fruits  drop  and  only  a  rather  low  percentage  of  the  total  num- 
ber of  original  blossoms  continues  to  develop.  It  is  quite  necessary  for 
this  drop  to  take  place,  as  the  tree  under  average  circumstances  would 
never  be  able  to  carry  so  many  fruits  through  to  maturity.  The 
factors  determining  which  of  these  young  fruits  shall  drop  are  not 
at  present  fully  known.  Later  in  the  season  there  takes  place  still 
another  falling  of  young  fruits  known  as  the  "June  drop." 

The  expression  normal  set,  is  a  more  or  less  technical  term  for 
designating  the  percentage  of  fruit  which  the  tree  sets  under  normal 
conditions  when  left  open  to  insect  pollination.  It  is  obvious  that  the 
normal  set  may  be  determined  at  any  time  up  to  the  end  of  the  season 
by  counting  the  fruits  on  a  tree  and  comparing  the  number  with  the 
original  bloom.  In  these  experiments  approximately  2000  blossoms 
of  each  variety  well  distributed  over  the  trees  were  counted  each  year 
and  proper  records  kept  to  determine  the  normal  set  after  the  first 
and  the  second  drop,  and  at  harvest  time. 

The  questions  at  once  arise  as  to  what  percentage  of  normal  set  at 
harvest  time  constitutes  a  full  crop  and  what  is  meant  by  a  "full 
crop."  What  constitutes  a  full  crop  of  any  fruit  is  perhaps  largely 
a  question  of  judgment  or  guess.  It  varies  with  such  factors  as 
variety,  soil  and  moisture  conditions.  What  would  be  considered  a 
full  crop  under  foothill  conditions  would  not  necessarily  be  the  same 
in  a  valley  location.  In  order  to  secure  some  idea  on  this  most  im- 
portant phase  of  the  subject,  table  II  is  herewith  presented  which 
gives  the  normal  set  of  certain  almond  varieties  for  the  years  1916 
and  1917,  together  with  the  average  yield  of  these  trees  reduced  to 
an  acreage  basis.  The  trees  under  observation  were  planted  during 
the  spring  of  1908,  being  set  twenty-four  feet  apart  by  the  square 


344  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 

system,  which  gives  approximately  seventy-five  trees  to  the  acre. 
Since  planting,  these  trees  have  received  good  commercial  culture. 
All  figures  given  are  based  on  the  yields  of  almonds  harvested. 

A  brief  examination  of  the  table  shows  that  too  much  stress  must 
not  be  laid  on  mere  percentages,  because  during  the  1916  season  the 
normal  set  was  much  heavier  than  in  1917,  but  the  crop  of  the  latter 
year  was  by  far  the  heavier.  This  is  easily  explained  by  the  relatively 
heavier  bloom  during  the  spring  of  1917.  These  figures  also  emphasize 
the  importance  of  correct  comparisons  and  show  that  the  normal  set 
must  be  carefully  taken  each  year  in  order  to  secure  a  correct  basis 
for  the  comparison  of  results  obtained  by  artificial  pollination. 

Table  II. — Comparison  of  Normal  Set  "With  Yield  of  Almonds 
IN  Pounds  (Dry  Weight)  per  Acre 

1916  1917 

A A 


r 

Percentage  Lbs.  per 

Variety  set  acre 

California  14  869.4 

Drake 15  1229.6 

Harriott    16  893.0 

I.  X.  L 17  1059.4 

Jordan  13  817.0 

King   29  660.4 

Languedoc    22  1763.4 

Lewelling   37  1235.0 

Ne  Plus  Ultra 26  1714.6 

Nonpareil  24  869.4 

Peerless  20  888.4 

Princess    17  935.0 

Beams   23  2044.4 

Texas    39  1657.6 


Percentage 
set 

Lbs.  per 
acre 

7.3 

865 

16.4 

3800 

11.9 

2240 

16.5 

1515 

3.6 

'   455 

25.7 

1395 

16.5 

745 

25.0 

2035 

20.4 

3670 

28.2 

2415 

7.0 

895 

17.7 

1275 

14.0 

2905 

21.7 

1430 

Average    22.3  1189.0  16.6  1885 

NORMAL    SET    OF   ALMOND    VARIETIES 

There  is  presented  in  table  III  a  record  of  the  normal  set  of  various 
almond  varieties  under  test  at  the  University  Farm.  It  will  be  noted 
that  the  normal  set  in  the  University  orchards  with  open  pollination 
ranged  all  the  way  from  3.6  per  cent,  in  the  case  of  the  Jordan  in 
1917,  to  39  per  cent  in  the  case  of  the  Texas  in  1916.  Probably  due 
to  unfavorable  weather  conditions  at  the  time  of  blossoming,  the  set 
during  1917,  on  the  whole,  was  somewhat  lower  than  that  of  the  pre- 
vious season,  the  average  being  16.6  per  cent  as  against  22.3  per  cent 
for  1916.     On  account  of  the  heavier  bloom,  however,  the  crop  was 


ALMOND   POLLINATION 


345 


considerably  heavier  than  during  the  preceding  season.  Attention 
is  also  called  to  the  fact  that  in  the  orchard  of  Mr.  G.  W.  Pierce 
(table  VI)  the  set  was  considerably  lower  than  at  the  University 
Farm.  This  is  explained  by  the  fact  that  in  Mr.  Pierce's  orchard 
practically  no  insect  pollen  carriers  were  present.  The  orchard  is 
properly  inter-planted  with  pollenizing  varieties. 


Table  III. — Normal  Set  of  Fruit  on  Almond  Varieties,  1916-1917 
University  Farm,  Davis,  California 


1916 

A 

1917 

A 

Variety 

No. 

blossoms 
counted 

No. 

fruits 
matured 

^ 

Percentage 
matured 

No. 
blossoms 
counted 

No. 

fruits 
matured 

Percentage 
matured 

Big  White  Flat 



1083 

154 

14.2 

California 

..       2402 

326 

14 

2707 

199 

7.3 

Drake 

..       2141 

336 

15 

2752 

453 

16.4 

Golden  State  

_. . 

•  .-• 

1044 

307 

30.0 

Harriott  

..       1961 

310 

16 

2301 

274 

11.9 

I.  X.  L 

.       2131 

363 

17 

2663 

433 

16.5 

Jordan   

1970 

249 

13 

2593 

94 

3.6 

King  

.       1675 

481 

29 

2512 

647 

25.7 

Klondike    



.... 

1069 

329 

30.4 

Languedoc  

..       2294 

503 

22 

2488 

419 

16.5 

Lewelling  

..       2151 

797 

37 

2653 

664 

25.0 

Ne  Plus  Ultra 

.       2071 

531 

26 

1953 

407 

20.4 

Nonpareil    

.       1989 

473 

24 

2647 

748 

28.2 

Peerless   

..       1975 

396 

20 

1925 

135 

7.0 

Princess  

..       2085 

356 

17 

2731 

456 

17.7 

Silver  Shell  

. . 

.... 

742 

136 

17.7 

Eeams  

..       1910 

443 

23 

2001 

280 

14.0 

Texas  

..       2019 

792 

39 

2568 

654 

21.7 

SELF-STERILITY    IN    VARIOUS    ALMOND    VARIETIES,     1916-1917 

Table  IV  gives  the  self-pollination  records  of  the  almond  varieties 
tested  for  self-sterility  during  1916  and  1917.  From  this  table  it 
will  be  noted  that  all  of  the  seventeen  varieties  tested  gave  distinct 
evidence  of  self-sterility.  The  Harriott  variety  in  1916  proved  self- 
fertile,  but  in  1917  was  decidedly  self-sterile.  The  probable  explana- 
tion is  that  this  is  a  variety  which  behaves  like  certain  varieties  of 
apples  and  pears  which  one  season  may  be  self-sterile,  while  another 
season  they  may  be  partly  self-fertile.  The  results  of  these  two 
seasons — 1916  and  1917 — and  also  for  1910  and  1911  are  the  same, 
viz.,  that  for  all  practical  purposes  the  cultivated  almond  is  self -sterile 
and  in  all  cases  orchards  must  be  inter-planted  with  pollenizing  varie- 
ties if  they  are  to  prove  commercially  profitable. 


346 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Table  IV. — Self-Pollination  of  Almond  Varieties,  1916-1917 
University  Farm,  Davis,  California 


No. 

blossoms 
self- 
Variety  pollinated 

Big  White  Flat 

California  1586 

Drake  996 

Golden  State  

Harriott    939 

I.  X.  L 740 

Jordan  819 

King    450 

Klondike  

Languedoc    979 

Lewelling    1031 

Ne  Plus  Ultra 1005 

Nonpareil  723 

Peerless  976 

Princess    822 

Reams   1064 

Texas  1029 


1916 

A 


No. 
fruits 
matured 


139 
4 
2 


1 

10 

6 

1 


Percentage 
matured 


.13 
.1 


15.0 
.5 
.2 


.1 

.97 

.6 

.14 


1917 

A 

No. 
blossoms 

self- 
pollinated 

No. 
fruits 
matured 

^ 

Percentage 
matured 

673 

17 

2.5 

464 

---. 

953 

---- 

554 

2 

.4 

1189 

1 

.08 

403 

1 

.25 

597 



900 

404 

2 

.49 

625 



960 

6 

.63 

327 

3 

.9 

446 

1 

.22 

237 

711 

.--- 

1015 

1 

.09 

994 

2 

.2 

CROSSES    BETWEEN    CERTAIN    ALMOND    VARIETIES 

Tables  V  and  VI  give  the  results  of  artificial  cross-pollination  dur- 
ing the  years  1916,  1917  and  1918. 


Table  V.— ' 

Cross-Pollination 

OF  Almond  Varieties, 

1916-1917 

University  Farm,  Davis,  California 

1916 

A 

1917 

A 

Variety 
California 

No. 

blossoms 

hand 
pollinated 

No. 
fruits 
matured 

^ 

Percentage 
matured 

No. 
blossoms 

hand 
pollinated 

No. 
fruits 
matured 

Percentage 
matured 

X  I.  X.  L 

.... 

211 

7 

3.3 

X  Jordan  

258 

15 

5.8 

X  Ne  Plus  Ultra . 

.... 

257 

10 

3.9 

X  Nonpareil 

250 

32 

12.8 

X  Peerless 

208 

17 

8.2 

Drake 

X  California    

.... 

505 

124 

24.6 

X  I.  X.  L 

.... 

514 

78 

15.1 

X  Jordan  

274 

65 

24  6 

X  Languedoc  

499 

73 

14.6 

X  Ne  Plus  Ultra 

.... 



980 

223 

22.8 

X  Nonpareil    

— 

450 

72 

16.0 

X  Peerless    

502 

89 

17.5 

X  Texas    

. 

511 

101 

20  0 

Harriott 

X  Ne  Plus  Ultra 

..-•.. 

— • 

568 

83 

14.6 

ALMoisfD  POLLINATION  347 

Table   V.— Cross-Pollination    of   Almond   Varieties,    1916-1917    (Continued) 

1916  1917 

, — A ^  , A 


No.  No. 

Variety                             blossoms  No.  blossoms  No. 

J    Tj-    T                                        hand  fruits       Percentage  hand  fruits  Percentage 

X.  -A.,  u.                              pollinated  matured  matured  pollinated    matured  matured 

X  Drake  ....  145  2  1.4 

X  Jordan   264  7  2.7 

X  Lewelling     ....  137  7  5.6 

X  Ne  Plus  Ultra ..       342  138  40  343  23  6.6 

X  Nonpareil  484  4  .8  412 

X  Peerless    ....  404  12  3.0 

Languedoc 

X  California    ....  502  65  12.9 

X  Drake  ....  429  64  14.9 

X  I.   X.  L ....  467  25  5.4 

X  Ne  Plus  Ultra ....  514  50  9.7 

X  Nonpareil    ....  471  23  4.9 

X  Peerless    ....  457  54  11.8 

X  Eeams ....  475  36  7.6 

X  Texas   ....  450 

Lewelling 

X  I.  X.  L ....  . 424  28  6.6 

X  Ne  Plus  Ultra ....  373  24  6.4 

X  Nonpareil    ....  244  18  7.5 

Ne  Plus  Ultra 

X  California  (P) ....  308  24  7.8 

X  Drake  -.  252  11  4.4 

X  Harriott  .-  266  26  9.7 

X  I.   X.   L 492  178  36                 (P)  477  88  18.4 

X  Jordan    (P) ....  160  20  12.5 

X  Lewelling  ....  287  24  8.4 

X  Nonpareil    482  80  17  223  28  12.5 

Nonpareil 

X  I.  X.  L 584  1  .17  283  1  .4 

X  Jordan   ....  401  65  16.2 

X  Lewelling    ■      .-  258  57  22.1 

X  Ne  Plus  Ultra ..       402  140  26 

Beams 

X  California    ....  306  50  16.7 

X  I.  X.   L ....  66  14  21.2 

X  Ne  Plus  Ultra ....  497  97  19.5 

X  Nonpareil    -  502  93  18.5 

X  Texas   .-  509  131  26.7 

Texas 

X  California    528  47  8.9 

X  Drake 478  79  16.5 

X  L   X.  L 394  76  19.6 

X  Languedoc  --  499 

X  Nonpareil    557  97  17.8 

Note. — (P)  m  above  table  indicates  that  crosses  thus  marked  were  performed 

in  the  Pierce  orchards. 


M8  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

Table  VI. — Crosses  on  the  Nonpareil  Almond,  1917-1918 
Pierce  Orchard,  near  Davis 


1917 

A 

1918 

A 

"Variety 
Nonpareil 

No. 

blossoms 

pollinated 

No. 
fruits 
matured 

Percentage 
matured 

No. 

blossoms 
pollinated 

No. 

fruits 

matured 

Percentage 
matured 

Normal  set  

.      3346 

94 

2.8 

2633 

42 

1.5 

Self -pollinated  

.       572 



356 

.... 

X  California    

.       392 

140 

35.7 

348 

27 

7.7 

X  Drake  

366 

47 

12.7 

370 

82 

22.0 

X  Eureka  

259 

23 

8.8 

X  Golden  State  ... 

292 

59 

20.2 

X  I.  X.  L 

.       237 

801 





X  Jordan  

226 

22 

9  7 

X  Languedoc  

.... 

477 

114 

23.9 

X  Ne  Plus  Ultra . 

.       406 

51 

12.5 

320 

78 

24.3 

X  Peerless 

396 

63 

15.8 

322 

53 

15  9 

X  Texas   

212 

63 

29.7 

409 

87 

21.2 

INTER-STERILITY  BETWEEN  ALMOND  VARIETIES 

In  all  the  reciprocal  crosses  made,  only  the  I.  X.  L.  and  Nonpareil 
and  the  Languedoc  and  Texas  varieties  seemed  to  give  distinct  evi- 
dence of  inter-sterility.  The  case  of  inter-sterility  between  Languedoc 
and  Texas  has  never  before  been  recorded,  so  far  as  the  writer  knows. 
The  inter-sterility  between  I.  X.  L.  and  Nonpareil  has  been  experi- 
mentally proved  in  1915,  1916,  1917  and  1918,  and  has  also  been 
experienced  in  practice  by  many  growers. 

The  parentage  of  almond  varieties  at  present  grown  in  California 
is  unknown  and  thus  it  is  impossible  to  attempt  an  explanation  of  the 
inter-sterility  of  these  varieties  on  the  basis  of  relationships. 

INFLUENCE    OF   POLLENIZERS    ON    CERTAIN    ALMOND    VARIETIES 

During  the  season  of  1916  reciprocal  crosses  were  made  only  be- 
tween the  Nonpareil,  I.  X.  L.,  and  Ne  Plus  Ultra  varieties  and  the 
results  showed  the  first  two  to  be  not  only  self -sterile  but  also  inter- 
sterile,  i.e.,  unable  to  pollinate  themselves  or  each  other.  The  Ne  Plus 
Ultra  fertilized  the  other  two  and  was  in  turn  successfully  fertilized 
by  them. 

More  than  50,000  artificial  cross-pollinations  were  made  during 
each  of  the  seasons  of  1917  and  1918.  The  entire  work  of  the  latter 
season  was  lost  by  frost  except  the  crosses  on  the  Nonpareil.  Like- 
wise on  account  of  unfavorable  weather  conditions  rather  negative 


ALMOND   POLLINATION  349 

results  were  obtained  with  certain  varieties  during  1917  and  conse- 
quently all  discussion  of  these  varieties  is  omitted.  For  the  sake  of 
brevity  there  has  also  been  purposely  left  out  of  this  publication  much 
of  the  data  collected,  only  sufficient  being  given  to  prove  each  point. 

It  is  hoped  that  sufficient  observations  and  experiments  may  be 
made  during  the  next  few  seasons  to  enable  the  Division  of  Pomology 
to  give  exact  information  regarding  the  planting  of  orchards  so  as  to 
insure  the  safe  pollination  of  any  variety  of  almond.  The  investiga- 
tion of  this  problem  has  been  confined  neither  to  the  varieties  at 
present  recommended  for  future  planting  nor  to  those  now  grown 
commercially  in  the  state,  a  consideration  of  several  kinds  of  minor 
importance  having  also  been  included.  In  making  recommendations 
of  varieties  for  interplanting,  the  writer  has  attempted  to  keep  in 
mind  the  date  of  blooming,  abundance  of  pollen  and,  to  a  limited 
extent,  the  productiveness  and  commercial  value  of  the  pollenizer.^ 

California. — The  Nonpareil  is  a  satisfactory  pollenizer  for  the 
California.  The  results  of  the  experiments  with  this  variety  have, 
up  to  the  present,  been  somewhat  negative. 

Drake. — Eight  varieties  in  all  were  used  as  pollenizers  for  the 
Drake,  all  of  which  gave  satisfactory  results.  These  varieties  were  the 
California,  I.  X.  L.,  Jordan,  Languedoc,  Ne  Plus  Ultra,  Nonpareil, 
Peerless  and  Texas.  Preference  should  be  given  to  the  California, 
Languedoc,  Nonpareil  and  Texas  varieties. 

Harriott. — The  Ne  Plus  Ultra  variety  is  a  satisfactory  pollenizer 
for  the  Harriott. 

7.  X.  L. — Little  weight  should  be  attached  to  the  results  of  the 
1917  season's  work  with  the  I.  X.  L.  variety  on  account  of  the  difficulty 
experienced  with  weather  conditions.  A  very  low  percentage  of  set 
was  obtained  with  the  pollen  of  all  varieties  used,  but  that  of  the 
Ne  Plus  Ultra  proved  the  most  satisfactory.  Nonpareil  pollen  failed 
both  seasons  to  set  fruit  on  the  I.  X.  L.  The  Ne  Plus  Ultra  variety 
may  be  recommended  for  pollenizing  the  I.  X.  L. 

Languedoc. — Of  the  eight  kinds  of  pollen  used  to  cross  with  the 
Languedoc,  that  of  the  California,  Drake  and  Peerless  varieties 
yielded  the  best  results.  Texas  pollen  set  no  fruit  on  the  Languedoc. 
On  account  of  its  coincidence  of  bloom  with  the  Languedoc  variety  the 
Drake  should  probably  be  recommended  as  a  pollenizer. 

Lewelling. — This  variety  was  crossed  with  only  three  kinds  of 
pollen — I.  X.  L.,  Ne  Plus  Ultra  and  Nonpareil,  and  none  of  these 

6  The  reader  will  find  a  comprehensive  discussion  of  the  proper  varieties  for 
the  commercial  plantation  in  Taylor 's  ' '  The  Almond  in  California, ' '  Bull.  No. 
297,  Calif.  Expt.  Sta. 


350  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 


c 


,£3 


»o  ® 


I         5      o 
I— O 

2  > 


OH  I 


F    ^  S$ 


o 


o 


.—I  «H 
O 

O 

02    R 


2  ^^ 


;-i    o 


.a 


^-  "'  03 


o 


03 
W 


89^0  I  I 


—  ^  :^    I         III  ^ 

OO  a.       la  h    _j  ^ 

^1  ^^a-s^l^ 


CO 


bX) 

•rH 


ALMOND   POLLINATION 


351 


§ 


o-» 


o 
Q 

s 

o 


<T> 

c 

1 

\_ 

^ 

:3 

o 

C 

.  q 

)0 

r 

"5 

E 
o 

o 

vO 

^ 

"> 

lA 

o 

<J 

Q 

CQ 

O 

I 

•*3 

-a 

c 

O 

1- 

o 

o 
O 

Ct 

1 

::r^ 

■«-> 

lO 

V. 

«> 

> 

:5 

S 

i 

llll.l 


I 


-J 


DC 
o 
tl- 


cs: 


^ 


IS^     5 


X 


u 


? 


CD 


•i     ^ 

o 


c 

O 

It 


-J 


o 


-J 


^ 

E 


Q'B 

u 

CD 

q-t  M 
o 
o 

qH  o 

(D 

o   g 

^    O 

c3    ^ 


1=1  "^S 

^    O 
w 

i-H 

la 


l-H 

an   (o 
o 

"I 

0) 
-(^  .Th 

O  «H 
Sn    CO 

=i  o 

fl 

•rH      gj 
O      S 

-*"  5« 

00  '*"' 

1^ 
^t 

"^ 

Eh  c« 


•00 
■*  o  o 

£   be  be 


352 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


-t-s 

•iH 

> 


X3 

Z 
o 

o 

o 

o 


^ 
^ 
a 


go 


t7- 


o 

S 
o 

^ 

\n 

^ 

CO 

o 

^ 

«\^ 

c 
o 


Ml 


I 


5 

o 


lU 

5  d.       li:  X 

o  -J      -J  cr 

s  Oo  c^  lU  o 


to 

Ci        J    - — I 

^   ^  x; 


(X 

i- 

o     ^ 

rr       "U      ^       M 


CI 


to 


^     dj      o 


o 

o 


X 


y 


PI    c3 
o  p^ 

^  o 
<=>  ? 

^^ 

o   o 

•r-l    r— I 
(-H    r— I 

Ph  o 

Pi    ft 
C^  . 

a^ 

(U       . 

^^ 

^     O 
O    . 

!»    cS 

^  PI 

d  -^ 

•iH 

1 1 

> 
o  ^ 

1 — I 
<D    O) 

^d 
P| 

03  4^ 

■+J  d 

ITS  «H 


I      '^ 
I      ^ 

•r-l 

bJO=H 
o 


ALMOND   POLLINATION 


353 


^      T^ 


CD 


O 

o 


o 


5:  '^ 


O   o 

o 


c 

CD 


CD 

> 

D 


00 

00 

O 

O 


o      ^ 


I 


o    da 


o       == 


-^   lu    a;    g  x;    "3:    ° 


a      .E 

c 

o 


o 


3  o 

O  JO 

O      o 

♦Q-      E  o 

>       o  ^ 


< 


O 


c 

Q     O 

0. 


> 
C 

3 


o 


:^ 


wo 


X 


en 
o 

O 


^73  d 
fl  o 


O    i=5 
O    o 

q:^   o 

Ph  t^ 
c3  -t^ 


rd 

05 


o 

O 

^g 

^^ 

•  S^ 

t»  d 
d;i:! 

is  ^ 

CO      I 
>•  «4H 

O    M 

rd 

■*^  d 

d  SH 

d  -^^ 

rd      '^ 
O   r-^ 

CO 

rd   m 

1.2 

go. 


354  UNIVERSITY    OF    CALIFORNIA — EXI'ERIMeNT    STATION 

yielded  even  one-third  as  high  a  set  as  the  insect-pollinated  flowers. 
(The  bees  had  easy  access  to  many  other  varieties  in  addition  to  the 
three  mentioned.) 

Ne  Plus  Ultra. — Pollen  from  eight  varieties  was  used  in  the  cross- 
ing experiments  with  Ne  Plus  Ultra.  California,  I.  X.  L.  and  Jordan 
gave  every  promise  of  being  exceedingly  good  pollenizers  for  the 
Ne  Plus  Ultra.  The  final  percentages  shown  in  the  table  should  not 
have  too  much  weight  due  to  the  fact  that  many  of  the  fruits  set  did 
not  come  to  maturity  on  account  of  mechanical  injury,  loss  in  culti- 
vation, etc.  The  Nonpareil  is  also  a  satisfactory  pollenizer  for  the 
Ne  Plus  Ultra  variety. 

Nonpareil. — Of  the  eleven  varieties  tested  as  pollenizers  for  the 
Nonpareil  only  the  I.  X.  L.  failed  to  set  a  crop.  During  1917  the 
California  was  preeminently  the  best.  During  the  1918  season  the 
Drake,  Ne  Plus  Ultra,  Texas  and  Languedoc  set  very  satisfactory 
crops  on  the  Nonpareil.  Preference  should  be  given  the  California, 
Drake,  Ne  Plus  Ultra  and  Texas  varieties. 

Beams. — The  Drake,  I.  X.  L.,  Ne  Plus  Ultra,  Nonpareil  and  Texas 
varieties  gave  entirely  satisfactory  results  as  pollenizers  for  the  Reams. 
Preference  should  be  given  the  Texas. 

Texas. — The  Drake,  I.  X.  L.  and  Nonpareil  varieties  gave  fair 
results  as  pollenizers  for  the  Texas,  although  the  percentage  set  in 
each  case  was  not  quite  equal  to  the  normal  set.  Pollen  of  the  Langue- 
doc variety  set  no  fruit  on  the  Texas. 

POLLENIZING  AGENCIES 

After  having  planted  inter-fertile  varieties  the  orchardist  should, 
by  all  means,  provide  an  agency  for  the  transfer  of  the  pollen  from 
the  trees  of  one  variety  to  those  of  another.  The  common  honey  bee 
is  by  far  the  best  carrier  of  pollen  and  it  will  pay  the  grower  to  keep 
bees  although  he  may  not  care  to  go  into  the  honey  business.  Bees, 
however,  are  a  very  profitable  side  line  for  the  orchardist,  especially 
if  alfalfa  fields  are  available  to  work  on  after  the  blooming  season  of 
fruit  has  passed.  About  one  hive  of  bees  to  an  acre  of  bearing  orchard 
should  be  provided.  Preferably  the  hives  should  be  scattered  as 
widely  as  possible  throughout  the  orchard  during  the  blooming  season. 
Experiment  and  experience  have  shown  that  little  reliance  can  be 
placed  on  the  efficacy  of  wind  and  insects,  other  than  the  honey  bee, 
in  effecting  the  transfer  of  pollen  from  tree  to  tree,  or,  in  fact,  from 
flower  to  flower. 


ALMOND   POLLINATION  355 

Eliminating  from  consideration  all  conditions  which  may  influence 
the  fruitfulness  of  an  orchard  except  those  occurring  at  blooming  time, 
it  may  be  said  that  the  set  is  largely  influenced  by  weather  conditions 
at  time  of  blooming.  Cold  weather,  aside  from  killing  the  blossoms  or 
lowering  the  vitality  of  the  pollen,  often  prevents  bees  from  working. 
The  same  would  be  true  if  cloudy,  wet  and  windy  weather  prevail. 
For  their  best  work  bees  demand  clear,  warm  and  quiet  days  and  since 
the  weather  at  the  time  almonds  bloom  is  often  quite  unsettled,  it  is 
readily  seen  that  the  blooming  period  of  the  various  poUenizing 
varieties  should  overlap  perhaps  a  week  in  order  that  there  may  be 
one  or  two  days  at  least  when  the  weather  will  be  favorable  for  insect 
pollination. 

As  a  case  in  point  mention  may  be  made  of  the  1917  blooming 
season  of  almonds.  Many  almond  growers  had,  during  this  season, 
a  light  crop — not  due  to  lack  of  proper  varieties,  nor  to  freezing  cold, 
but  due  to  the  existence  of  such  weather  conditions  throughout  the 
blooming  period  that  the  bees  were  prevented  from  working.  This 
point  further  illustrates  the  great  necessity  of  having  in  the  orchard 
a  large  number  of  these  ''helpers. 


J  7 


ARRANGEMENT   OF  THE   ORCHARD    FROM    A    POLLINATION    STANDPOINT 

In  planting  an  orchard  it  is  desirable  to  have  at  least  every  sixth 
and  preferably  every  fourth  row  of  a  pollenizing  variety.  For  con- 
venience in  harvesting,  it  is  best  to  plant  two  rows  of  one  kind,  then 
two  rows  of  the  pollenizing  variety,  and  so  on;  or,  if  it  is  desired  to 
have  more  of  one  variety  than  another,  four  rows  of  the  favorite 
variety  and  then  two  rows  of  the  pollenizer,  and  repeat.  For  various 
reasons,  it  is  often  desirable  to  reduce  the  number  of  pollenizing  trees 
to  the  minimum.  Under  these  circumstances,  one  tree  in  twenty-five 
is  perhaps  sufficient,  although  at  least  one  tree  in  eight  is  strongly 
recommended.  It  is  seldom  wise  to  graft  over  a  part  of  a  tree  to  the 
pollenizing  variety  as  this  tends  towards  confusion  and  expense  in 
harvesting. 

In  planting  one  tree  of  the  pollenizer  to  seven  or  eight  of  the  main 
variety,  the  pollenizer  should  be  placed  as  every  third  tree  in  every 
third  row  in  such  a  way  that  the  spaces  in  the  pollination  rows  are 
broken  as  shown  on  the  following  page,  the  o  in  each  case  representing 
a  pollenizer  tree. 

If  by  chance  a  self -sterile  variety  has  been  planted  in  a  solid  block, 
the  necessary  pollinator  may  be  introduced  by  grafting.  Some  relief 
may  be  obtained  during  the  years  while  waiting  for  the  trees  grafted 


356 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 


over  to  pollenizing  varieties,  to  come  into  bearing,  by  cutting  off  large 
limbs  of  pollenizing  varieties,  placing  the  cut  ends  in  buckets  of 
water  and  distributing  the  same  throughout  the  orchard  during  the 
blooming  period.  Such  limbs  will  live  for  several  days  and  continue 
to  bloom,  forming  pollen  for  the  bees  to  transfer  to  the  self-sterile 
variety.  \ 


SUMMARY   OF  ALMOND    POLLINATION 

1.  Satisfactory  artificial  germination  of  almond  pollen  was  secured 
in  a  12  per  cent  cane  sugar  solution. 

2.  Inclement  weather  conditions  undoubtedly  injured  the  viability 
of  the  almond  pollen  produced  during  the  blooming  seasons  of  1917 
and  1918. 

3.  There  is  considerable  variation  in  the  amount  of  pollen  pro- 
duced by  the  various  almond  varieties. 

4.  Almond  varieties  may  be  roughly  divided  into  two  classes :  earlj^ 
bloomers  and  late  bloomers,  when  the  length  of  their  effective  full 
bloom  is  considered. 

5.  The  first  blossoms  produced  by  certain  almond  varieties  each 
season  may  yield  a  smaller  amount  of  pollen  and  pollen  which  is 
inferior  in  viabilitj^  to  that  produced  by  flowers  on  the  same  tree 
maturing  several  days  or  a  week  later. 

6.  Pollenizing  agencies,  such  as  the  honey  bee,  are  necessary  to  the 
set  of  a  good  crop  of  fruit. 

7.  The  Harriott  variety,  which  during  the  season  of  1916  proved 
able  to  set  fruit  with  its  own  pollen,  the  following  season  proved  self- 
sterile. 

8.  All  almond  varieties  thus  far  tested  have  proved  self-sterile,  at 
least  in  certain  years.     All  of  the  seventeen  varieties  tested  during 


ALMOND   POLLINATION  357 

the  season  of  1917  proved  self-sterile.     This  list  includes  the  Big 
White   Flat,    California,   Drake,    Golden   State,   Harriott,   I.   X.   L., 
Jordan,  King,  Klondike,  Languedoc,  Lewelling,  Ne  Plus  Ultra,  Non- 
pareil, Peerless,  Princess,  Reams,  Texas  and  a  hardshell  seedling. 
9.  Certain  almond  varieties  are  inter-sterile. 

10.  The  I.  X.  L.  and  Nonpareil  varieties  proved  practically  inter- 
sterile  during  the  two  seasons'  work. 

11.  The  Languedoc  and  Texas  are  inter-sterile,  as  shown  by  the 
results  of  1917. 

12.  The  California  at  present  seems  to  be  the  one  best  pollenizer 
for  all  varieties  thus  far  tested,  which  have  a  coincident  period  of 
bloom. 

13.  The  California  may  be  pollinated  by  the  Nonpariel  and  Peerless. 

The  Drake  may  be  pollinated  by  the  California,  Languedoc, 

Nonpareil  and  Texas ;  however,  the  Languedoc  is  a  poor 

pollen  producer. 
The  Harriott  may  be  pollinated  by  the  Ne  Plus  Ultra. 
The  7.  X.  L.  may  be  pollinated  by  the  Ne  Plus  Ultra. 
The  Languedoc  may  be  pollinated  by  the  Drake. 
The  Ne  Plus  Ultra  may  be  pollinated  by  the  California, 

I.  X.  L.,  Jordan  and  Nonpareil. 
The  Nonpareil  may  be  pollinated  by  the  California,  Drake, 

Jordan,  Ne  Plus  Ultra,  Peerless,  and  Texas. 
The  Reams  may  be  pollinated  by  the  Texas. 
The  Texas  may  be  pollinated  by  the  Drake  and  Nonpareil. 

14.  One  colony  of  honey  bees  should  be  provided  for  each  acre 
of  orchard. 

15.  Care  should  be  taken  in  the  arrangement  of  varieties  in  the 
orchard  to  facilitate  cross-pollination  and  convenience  in  harvesting. 

ACKNOWLEDGMENTS 

The  writer  wishes  to  express  his  appreciation  of  the  assistance  he 
has  received  from  students  and  colleagues.  Messrs.  M.  B.  Weidenthal 
and  Henry  Schlapp,  senior  students  in  the  University  of  California, 
performed  certain  phases  of  the  work  as  thesis  problems,  and  without 
their  help  it  would  have  been  impossible  to  have  made  so  many  pol- 
linations. Messrs.  M.  N.  "Wood,  G.  L.  Philp,  and  Miss  R.  M.  Ames- 
bury,  members  of  the  Division  of  Pomology,  also  rendered  invaluable 
assistance  in  the  field  and  laboratory.  Dr.  W.  L.  Howard,  also  of  this 
Division,  has  given  great  service  in  suggestions  and  criticisms. 
Mr.  Geo.  W.  Pierce  kindly  allowed  the  use  of  his  orchard  for  certain 
experiments  which  could  not  be  carried  out  in  the  University  orchards. 


358 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


Fig.  7. — Only  two  fruits  from  349  blossoms  left  open  to  natural  conditions 
(normal  set).  Only  that  portion  of  the  branch  bearin<^  fruit  is  shown  in  the 
photograph.    A  typical  example  of  the  normal  set  in  the  Pierce  orchard,  1918. 


ALMOND  POLLINATION 


359 


Fig.  8. — No  fruit  set  on  branch  of  Nonpareil  which  was  pollinated  with  its 
own  pollen.  Twenty-eight  blossoms  set  no  fruit.  A  typical  cluster  of  Nonpareil 
when  self-pollinated.    Pierce  orchard,  1918. 


360 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


Fig.  9. — Six  Nonpareil  fruits  set  from  fifteen  blossoms  pollinated  with  Cali- 
fornia pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with  Cali- 
fornia.    Pierce  orchard,  1918. 


ALMOND   POLLINATION 


361 


Fig.  10. — Twelve  Nonpareil  fruits  set  from  thirty-one  blossoms  pollinated 
with  Golden  State  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil 
with  Golden  State.     Pierce  orchard,  1918. 


362 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  11. — No  fruits  sot  on  branch  of  Nonpareil  which  was  pollinated  with 
I.  X.  L.  pollen.  Fifteen  blossoms  set  no  fruit.  A  typical  cluster  resulting  from 
crossing  Nonpareil  with  I.  X.  L.     Pierce  orchard,  1918. 


ALMOND   POLLINATION 


363 


Fig.  12. — Fifteen  Nonpareil  fruits  set  from  twenty-eight  blossoms  pollinated 
with  Languedoc  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with 
Languedoc.     Pierce  orchard,  1918. 


364  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  13. — Fourteen  Nonpareil  fruits  set  from  twenty-nine  blossoms  pollinated 
with  Ne  Plus  Ultra  pollen,  A  typical  cluster  resulting  from  crossing  Nonpareil 
with  Ne  Pius  Ultra.     Pierce  orchard,  1918. 


ALMOND   POLLINATION 


365 


Fig.  14. — Nine  Nonpareil  fruits  set  from  twenty  blossoms  pollinated  with 
Peerless  pollen.  A  typical  cluster  resulting  from  crossing  Nonpareil  with  Peer- 
less.    Pierce  orchard,  1918, 


366 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 


Fig.  15. — Twelve  Nonpareil  fruits  set  from  twenty-nine  blossoms  pollinated 
with  Texas  pollen,  A  typical  cluster  resulting  from  crossing  Nonpareil  with 
Texas.     Pierce  orchard,  1918. 


